The present invention relates to a rubber composition and a pneumatic tire.
Aromatic oil has been conventionally used as a plasticizer in a rubber composition for a tire, however, since aromatic oil is required to be replaced because of carcinogenicity problem and the like, respective tire companies are going to implement countermeasure in Japan at present to a direction of changing to use various oils (alternative aromatic oil) derived from petroleum having a similar structure. However, the alternative aromatic oil also still depends on petroleum resources. Further, when petroleum oil is compounded in a rubber composition containing a natural rubber in particular, rolling resistance of tires is increased (rolling resistance property is deteriorated) and fuel cost tends to be poor. Further, both of the aromatic oil and alternative aromatic oil still have problems to be improved in performance such as filler dispersibility, abrasion resistance in tread use and crack resistance in sidewall use, in particular, in a rubber composition containing a natural rubber, in particular, a rubber composition containing a natural rubber and silica.
Further, global environmental problems have been recently emphasized and since a new plasticizer replacing the petroleum oil has been required, it is preferable to replace it with a vegetable oil and the like which are ecological to environments. JP-A-2003-64222 discloses a rubber composition containing a vegetable oil and fat such as a soy bean oil and a palm oil. This is excellent in the viewpoint of considering environments, but abrasion resistance, filler dispersibility and crack resistance were greatly inferior in comparison with a case of compounding an aromatic oil.